When the listing specifies not to choose Vinted Go and the buyer chooses it anyway; since I don’t want to spend my time fruitlessly looking for a locker for 10 euros, what would you do in my place? Should I try to post it once and if I don’t find a spot, just give up? PS: He tells me he had no carrier choice.
Hello,
As shipping options are regularly restricted for buyers, I will take the time to drop the package at a Vinted Go point, but I am in a large city with several options if needed. 
(Several lockers for Mondial Relay and Vinted Go, and Shop2shop relay points)
As usual, no lockers available. I cancelled the order at the buyer’s request.
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Hello
Since you cancelled the transaction, it’s a bit late but you could have perhaps checked with the buyer to help them verify the available carriers… if they are new to this, it’s possible they don’t know how to select another one…
He told me he only had that choice.
I sell but I also buy and confirm that when buying, I don’t always have a choice of carrier.